Process for printing textile fabrics with vat dyes



Patented Mar. 4, 1952 2,587,905 ICE PROCESS FOR PRINTING TEXTILE FABRICS WITH VAT DYES Arthur K. Saville, Wilmington, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware" No Drawing. Application September 14, 1950, Serial No. 184,901

1 Claim.

1 This invention relates to an improved process of printing textile fabrics with vat colors, and more particularly to a process whereby piece goods can be printed with vat dyes in a continuous manner.

Vat dyestuffs are conventionally printed from a starch-gum thickener which contains alkali carbonates and sodium sulfoxylate formaldehyde. These prints are dried after printing and aged for periods of up to 12 minutes in an air-free steam atmosphere and subsequently oxidized and soaped. By this technique only selected vat dyes are printable. Unfortunately, many of the faster anthraquinone types are poorly developed and the color selection is limited to the more easily fixed, more fugitive thioindigoid and indigoid and selected anthraquinone dyes.

I have found that excellent fixation in general of vat dyes on fabrics results when thickened vat dye pigments are printed, dried and impregnated with alkali and reducing agents in a conventional chemical padder and then led through a steam chamber for periods of ten to sixty seconds. By this method development of the dyes and fixation on the fabric is excellent. However, there results considerable bleeding or flushing of the colors as well as marking off of the color from the face of the print to the padder roll. In addition, during the expression of excess liquor from the fabric by the padder, appreciable amounts of dyestuff bleed into the impregnation solution and subsequently stain the white unprinted portions of the fabric. When vat dye pigment prints are padded in this manner, prints of diffuse outline with undesirably stained white areas are obtained.

Previous inventors have endeavored to reduce the flushing, bleed and mark off of the dyestuff during the padding operation by using alkali co agulable thickeners as printing vehicles. Unfortunately, unsatisfactory penetration of the print by the reducing solution is obtained with the result that development of the color during a short steaming is poor.

U. S. Patent 1,710,007 describes the use of methyl cellulose as a thickener for vat dye pastes which are printed on cellulosic fabrics. The fabric is dried and padded with a liquor consisting of sulfoxylates and potash. The material is then dried and steamed in a conventional rapid ager for five minutes. The deficiencies of this process are that only dyestuffs which can be developed by the conventional printing process can be used and the time of development to fix the dye is not significantly reduced. Furthermore,

color development of prints made with methyl cellulose thickeners are inferior to prints made with conventional thickening agents, unless steaming times are greatly increased.

It is an object of this invention to provide for a process of printing vat dyes on fabrics in a rapid manner and a process which may be adapted as a continuous process if desired. It is a further object of this invention to provide for such a process without the heretofore attendant bleeding, flushing or marking off of the printed colors but on the contrary to provide for such a process which results in clear, sharp and distinct printed color areas. A further object is to provide for such a process which is applicable to most if not all vat dyes and not merely to the heretofore considered printable vat colors.

I have found that these objects may be attained by printing the vat colors on the cloth in pigment form and in a thickened paste, as more particularly illustrated in the examples, drying, overprinting the entire fabric with an aqueous solution of caustic alkali and sodium hydrosullite, and then within twenty seconds of such overprinting passing the goods into an air-free steam chamber such as the Mather-Flatt type whereby reduction and fixation of the printed vat dye takes place. From the steam chamber the fabric is subjected to the usual oxidation, rinsing, soaping, rinsing and drying operations, all of which may be carried out in a continuous manner as desired.

The vat dye pigments may be printed by conventional printing equipment such as described in The Principal and Practices of Textile Printing, Knecht and Fothergill, 3rd edition, 1936.

In practice, I have found that a low solids thickener (i. e., containing 0.5% to 6% solids) such as is exemplified by sodium alginate, sodium carboxy methyl cellulose, and locust bean powder is most satisfactory for this purpose. These thickeners print satisfactorily and have the advantage of not inhibiting the penetration of reducing agents and alkali when the prints are subsequently overprinted. Other thickeners such as starch, British gum (dextrin) and textile gum give less sharp prints and inferior color value. Fabrics may be dried for after-printing by any suitable means such as flue driers or cans.

In the overprinting step the alkali and sodium hydrosulfite are applied from a thickened aqueous solution by means of a suitable blotch or stipple engraved roller in order to apply such reagents evenly over the whole surface of the fabric. This step is similar to other techniques whereby the whole surface of the fabric is treated with chemicals or other agents. The amount of the reagent applied may be varied at will by choice of suitable depths of engraving on the engraved roller so as to regulate the quantity of the gum applied. For example, the deeperthe engraving the heavier the application of the agent. It is necessary of courseto apply suflicient alkali and hydrosulfite in order to completely reduce the vat dye during the steaming operation. The precise quantities employed will depend on the strength parts of British gum and parts of water is satis factory. I

i It is-important to expose the overprinted fabric totheaction of the steamas soon as possible afteroverprinting; however, small variations from the time of overprinting and entering the steam chamber are-not critical if the totaltimeof exposure-to air is less than seconds. Intimes.

longer than this excessive decomposition of the reducing agent will occur with the result that incomplete reduction and. fixationof the dyestuif' will result inthe steamer.

.The' fabric should be treated inanair-free steam atmosphere at a temperature of approximately 212 F. It is undesirable to have excessive amounts-of condensateinthesteam or excessive condensation of moisture on the. fabric will occur. Nor should the steam be super-heated or the colorv will be over-reduced with the color of poor fixation- It is necessary to have an airfree steam atmosphere inthis process or the hydrosulfite will-be decomposed. The steam normally available: in textile processing plants may be considered sufliciently air-free for this pur' pose. The time of steaming must be sufiicient to allow dyeing with the color on the fabric; Times below 5' seconds maybe operable withspecific colors but are not generally acceptable.

fixation of any vat colors.

oxidizing and soaping of the steamed prints follows conventional textile processing procedures. Thefollowing examples. are given to further illustrate my invention. The parts given are by Weight, unless otherwise indicated.

v EXAMPLE 1 Cotton poplin is printed with the following printing color by machine printing:

100 grams blue dyestuff, Color Index 10011113 200 grams water 700 grams ThickenerA 1000 grams total Thickener'A 33i00 gra-mssodiumalginate 958.25gr'ams water 8.00 grams sodium tetraphosphate- .25 gram .Shirlan A1- .50 gram ammonia 1000.00 grams total 1 An aqueous dispersion of salicyl anilide with Daktose (deacetylated chitin), acetic acid and aluminum triacetate, used to prevent mildew.

After printing and drying the material is blotch printed with the following solution:

'70' grains caustic soda 70 grams sodium hydrosulfiter 860 gramsThickenerB;

1000-grams total Times above seconds are not necessary to completev ThickenerB:

grams wheat starch 300 grams British gum 600 grams water 1000 grams total Cook for /2 hour.

After blotch printing the material is led immediatelyinto an air-free steam atmosphere and steamed for 20 seconds at 212 F., rinsed in cold water, oxidized in 2.0% hydrogenperoxide, acidifi'ed with acetic acid and washed and soaped at the boil.

EXAMPLE 2 Cotton sateen is printed with. the'followin printing color:

100 grams yellow dyestuff, Color Index No.1118 200 grams water 700 gramsThickener A 1000'grams total The fabric is dried and treated asdescribedin: Example 1.

EXAMPLEB Cotton poplin is printed with the following printing color:

100 grams red dyestufl, Pr. 124 200 grams water '700 grams Thickener A M 1000 grams total The fabric is dried and treated'as'describedin' Example 1.

In each of the above examplsclear and distinct printings are obtained, for there is no evidence of bleeding or flushing of the printed colors nor is there found any staining of the white portions of the fabric. Furthermore, the true potential color value and brilliance of the'vat colors are obtained by the process described.

On the other hand, the following example'of the conventional alkali carbonate-sodium sulfoxylate formaldehyde method of'printing resulted in a considerably inferior'strength' of print as compared to the process of my invention exemplified in Example 1 in which the same vat dye is used. It is to be noted also that the steaming timeis considerably longer in the' followingexample.

EXAMPLE .4

The cotton sateen fabric is printed-withthe following printing color:

100 grams blue dyestufi, Color. Index No. 1113 900 grams Thickener C 1000 grams total Thickener C grams sodium formaldehyde sulfoxylate 120 grams potassium carbonate 760 grams starch British gum thickener 1000 grams total 7 The printed fabric is dried, agedfi-minutesdn anLair-free steam atmosphere, oxidized: in sodiumperoxide, acidified :with; acetieacid: ancksoaped? at the boil.

By the process :of the present-:dnrrention one is :not limited to. the use: 0f;ce11ulosei' others ands esters in the dye paste nor must one use sulfoxylate-potash mixtures, but instead one finds sodium hydrosulfite-caustic alkali mixtures to be most eflective. The process has the additional advantage of being adaptable to the use of any vat dye and allows fixing such dye on the fabric by short steaming of the order of 20 seconds. Thus, by the use of caustic alkalies and sodium hydrosulfite it is possible to decrease considerably the length of time in the steamer necessary to reduce and fix the dyestuil. In addition, a large number of vat dyes particularly of the anthraquinone class are reduced and fixed with greatly improved strength and brilliance over the conventional methods.

The process of this invention is applicable to cotton and to any of the cellulose or other fibers normally dyed with vat dyes.

In addition to the advantage of providing a rapid and satisfactory method of printing vat dyes, my invention also produces other advantages. Prints can be made and stored until some convenient time for developing and finishing. Dyestuffs not normally printed can be satisfactorily applied thereby allowing faster dyes to be used and better color value is generally obtained from the dye and with the increase of the tinctorial strength being demonstrated there is a resultant saving in the amount of dye used. Not to be overlooked, also, is the fact that ii mistakes are made in printing the goods can be secured, recovered and reprinted since the vat lose, and locust bean powder, drying, overprinting the entire fabric with a thickened aqueous solution containing 2% to 10% caustic alkali and 2% to 10% sodium hydrosulfite wherein the ratio of hydrosulfite to caustic alkali is between the limits of 0.5 to 3.0, and passing the fabric Within 20 seconds from the time it is overprinted into an air-free steam chamber for a period between 5 seconds and seconds to eifect reduction and fixation of the printed dye on the fabric.

ARTHUR K. SAV'ILLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,870,516 Kunz Aug. 9, 1932 2,069,919 Hardacre Feb. 9, 1937 2,089,920 Aubauer Aug, 10, 1937 2,487,197 Stott Nov. 8, 1949 

